Devices installed in industrial vehicles such as wheel loaders having a torque converter include those lead, as operation oil, pressurized oil from a hydraulic pump to a torque converter and lead, as clutch control pressure, pressurized oil to a control valve for clutch control of a transmission (see, for instance, patent reference literature 1). In the device described in patent reference literature 1, a pressure regulation valve is provided so that clutch control pressure supplied to the control valve becomes a predetermined set pressure, thereby leading pressurized oil exceeding the set pressure that has passed through the pressure regulation valve to the torque converter, and leading pressurized oil that has passed through the torque converter to an oil cooler. A safety valve is placed between the pressure regulation valve and the torque converter so as to limit the pressure at the entrance of the torque converter, thereby returning oil that has passed through the safety valve to a reservoir.    Patent reference literature 1: Japanese Laid Open Patent Publication No. 2005-163979 (FIG. 2)